Motor assembly for starting engine and driving balance shaft and method of controlling the same

ABSTRACT

A method of controlling a motor assembly for starting an engine and driving a balance shaft includes: determining whether starting or restarting of an engine is desired; operating an actuator such that a motor shaft is moved forward when the starting or restarting of the engine is desired; and starting or restarting the engine by rotating a motor and by driving a start gear, after the operating the actuator.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of non-provisional U.S.patent application Ser. No. 15/228,033, filed on Aug. 4, 2016, whichclaims priority to and the benefit of Korean Patent Application No.10-2015-0142156, filed on Oct. 12, 2015, the entirety of each of whichare incorporated herein by reference.

FIELD

The present disclosure relate to a motor assembly for starting an engineand driving a balance shaft, and a method of controlling the same.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

A balance shaft is a device for reducing vibration and noise generatedby the reciprocating motion of a piston and the rotary motion of acrankshaft when an engine rotates. That is, the balance shaft rotates ina direction opposite to the crankshaft so as to cancel out vibration andnoise generated by the rotary motion of the crankshaft. A mechanicalbalance shaft and a motor-driven balance shaft are used as examples ofsuch a balance shaft.

Since the mechanical balance shaft is connected to the crankshaft of anengine by chains, gears, or the like, it is always driven regardless ofan engine speed. However, the balance shaft requires a high engine speedequal to or higher than 4000 RPM, at which inertial force due to thereciprocating mass of the engine, e.g. a piston, is rapidly increased.For this reason, if the balance shaft is always driven, fuel efficiencymay be very poor.

In order to address this issue, the motor-driven balance shaft, which isdriven only in a high engine speed range by controlling the operation ofa motor, is developed. However, the motor-driven balance shaft requiresa separate motor, a motor control unit, and a power supply. For thisreason, there is an issue in that the cost and weight of the balanceshaft are increased and a separate space must be provided within anengine room.

In addition, since a starter motor for an ISG (Idle Stop and Go) systemis used only to start or restart an engine, it is rarely utilized.

SUMMARY

The present disclosure provides a motor assembly for starting an engineand driving a balance shaft, in which a balance shaft for reducinginertial force due to reciprocating mass of an engine and a startermotor for performing an ISG (Idle Stop and Go) function are combined asa single system, and a method of controlling the same.

In one form of the present disclosure, a motor assembly for starting anengine and driving a balance shaft includes a motor (100) for rotating amotor shaft (110) which is axially movable, a clutch (200) attached toone end of the motor shaft (110) so as to transfer or block rotationalforce of the motor shaft (110), a balance shaft (300) rotated by therotational force of the motor shaft (110) transferred through the clutch(200) so as to reduce vibration generated by an engine (1), a start gear(400) attached to the other end of the motor shaft (110); and anactuator (500) for axially moving the motor shaft (110) in a forward orbackward direction.

The motor (100) may be a permanent magnetic AC motor with a vectorcontrol function.

The balance shaft (300) may not be connected to a crankshaft of theengine (1).

The actuator (500) may be a shift actuator.

The actuator (500) may axially move the motor shaft (110) in the forwardor backward direction in order to simultaneously control forward orbackward movement of the start gear (400) and disengagement orengagement of the clutch (200).

The motor assembly may further include a ring gear (600) engaged withthe start gear (400) by the forward movement of the start gear (400) soas to transfer the rotational force of the motor shaft (110) to theengine (1).

The ring gear (600) may be arranged within a transmission (3).

In accordance with another form of the present disclosure, a method ofcontrolling a motor assembly for starting an engine and driving abalance shaft includes determining whether it is desired to start orrestart an engine (1) (S100), operating an actuator (500) such that amotor shaft (110) is moved forward (S200) when it is desired to start orrestart the engine (1), and starting or restarting the engine byrotating a motor (100) and driving a start gear (400) (S300), after theoperating an actuator (500) (S200).

In the operating an actuator (500) (S200), a clutch (200) may bedisengaged while the start gear (400) is engaged with a ring gear (600).

The method may further include stopping operation of the actuator (500)such that the motor shaft (110) is moved backward (S400) when it is notdesired to start or restart the engine (1).

In the stopping operation of the actuator (500) (S400), a clutch (200)may be engaged while the start gear (400) is disengaged from a ring gear(600).

The method may further include determining whether an RPM of the engine(1) is less than a predetermined target RPM (S500), after the stoppingoperation of the actuator (500) (S400).

The method may further include driving a balance shaft (300) by rotatingthe motor (100) (S600) when the RPM of the engine (1) is equal to orhigher than the predetermined target RPM.

Further areas of applicability will become apparent from the descriptionprovided herein. It should be understood that the description andspecific examples are intended for purposes of illustration only and arenot intended to limit the scope of the present disclosure.

DRAWINGS

In order that the disclosure may be well understood, there will now bedescribed various forms thereof, given by way of example, referencebeing made to the accompanying drawings, in which:

FIG. 1A and 1B are block diagrams illustrating a motor assembly forstarting an engine and driving a balance shaft according to one form ofthe present disclosure;

FIGS. 2 to 4 are views illustrating the operational state of the motorassembly for starting an engine and driving a balance shaft; and

FIG. 5 is a flowchart illustrating a method of controlling a motorassembly for starting an engine and driving a balance shaft according toanother form of the present disclosure.

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses. Itshould be understood that throughout the drawings, correspondingreference numerals indicate like or corresponding parts and features.

On the basis of the principle that the inventor can define theappropriate concept of a term in order to describe his/her own presentdisclosure in the best way, it should be construed as meaning andconcepts for complying with the technical idea of the presentdisclosure. Accordingly, the forms described in the presentspecification and the construction shown in the drawings are nothing butone form of the present disclosure, and it does not cover all thetechnical ideas of the present disclosure. Thus, it should be understoodthat various changes and modifications may be made at the time of filingthe present application. In addition, detailed descriptions of functionsand constructions well known in the art may be omitted to avoidunnecessarily obscuring the gist of the present disclosure.

FIGS. 1A and 1B are block diagrams illustrating a motor assembly forstarting an engine and driving a balance shaft according to one form ofthe present disclosure. Referring to FIGS. 1A and 1 B, the motorassembly for starting an engine and driving a balance shaft includes: amotor 100, a clutch 200, a balance shaft 300, a start gear 400, anactuator 500, and a ring gear 600.

The motor 100 serves to rotate a motor shaft 110 which is axiallymovable. The balance shaft 300 may be rotated (driven) through theclutch 200 connected to one end of the motor shaft 110, and an engine 1may be started through the start gear 400 connected to the other end ofthe motor shaft 110. In addition, the motor 100 may be a permanentmagnetic AC motor with a vector control function. This enables therotational speed and phase of the balance shaft 300 to be accuratelycontrolled.

The clutch 200 is attached to one end of the motor shaft 110, and servesto transfer the rotational force of the motor shaft 110 to the balanceshaft 300 or block the same.

The balance shaft 300 is rotated by the rotational force of the motorshaft 110 transferred through the clutch 200, and serves to reducevibration generated by the engine 1. In addition, the balance shaft 300may be disconnected from the crankshaft of the engine 1. That is, thebalance shaft 300 may not be driven when the RPM of the engine 1 is lessthan a predetermined target RPM, unlike a conventional mechanicalbalance shaft which is connected to the crankshaft of an engine bychains, gears, or the like to be always driven regardless of an enginespeed. Thus, the fuel efficiency of the vehicle can be improved.

The start gear 400 may be attached to the other end of the motor shaft110. In addition, the start gear 400 may be engaged with or disengagedfrom the ring gear 600.

The ring gear 600 is engaged with the start gear 400 by the forwardmovement of the start gear 400, so as to transfer the rotational forceof the motor shaft 110 to the engine 1. In addition, the ring gear 600may be arranged within a transmission 3.

The actuator 500 serves to axially move the motor shaft 110 in a forwardor backward direction. In addition, the actuator 500 may be a shiftactuator (especially, a bidirectional shift fork actuator). The actuator500 axially moves the motor shaft 110 in the forward or backwarddirection, so as to simultaneously control the forward or backwardmovement of the start gear 400 and the disengagement or engagement ofthe clutch 200. That is, when the actuator 500 is operated, the motorshaft 110 is axially moved forward, and thus the start gear 400 is alsomoved forward while the clutch 200 is disengaged. In addition, when theoperation of the actuator 500 is stopped, the motor shaft 110 is axiallymoved backward (i.e. the motor shaft 110 is returned to the originalstate), and thus the start gear 400 is also moved backward while theclutch 200 is engaged.

FIGS. 2 to 4 are views illustrating the operational state of the motorassembly for starting an engine and driving a balance shaft according tothe form of the present disclosure. Referring to FIG. 2, when the engineis intended to be started or restarted, the actuator 500 is firstoperated such that the motor shaft 110 is moved forward. Thus, the startgear 400 is engaged with the ring gear 600 while the clutch 200 isdisengaged. The rotational force of the motor 100 is then transferred tothe ring gear 600 so that the engine 1 is started or restarted.

Referring to FIG. 3, when the RPM of the engine 1 is less than apredetermined target RPM, the actuator 500 is operated such that themotor shaft 110 is moved backward. Thus, the start gear 400 isdisengaged from the ring gear 600 while the clutch 200 is engaged. Atthe same time, the motor 100 is stopped, and thus both of the ring gear600 and the balance shaft 300 are not driven.

Referring to FIG. 4, even when the RPM of the engine 1 is equal to orhigher than the predetermined target RPM, the actuator 500 is operatedsuch that the motor shaft 110 is moved backward. Thus, the start gear400 is disengaged from the ring gear 600 while the clutch 200 isengaged. The motor 100 is then rotated, and the rotational force of themotor 100 is transferred to the balance shaft 300 through the clutch 200so as to drive the balance shaft 300.

FIG. 5 is a flowchart illustrating a method of controlling a motorassembly for starting an engine and driving a balance shaft according toanother form of the present disclosure. Referring to FIG. 5, the methodof controlling a motor assembly for starting an engine and driving abalance shaft includes: a first determination step of determiningwhether it is desired to start or restart an engine 1 (S100); a firstoperation step of operating an actuator 500 such that a motor shaft 110is moved forward (S200) when it is desired to start or restart theengine 1; and an engine start or restart step of rotating a motor 100rotates to drive a start gear 400 (S300) after the first operation step(S200). In step S200, a clutch 200 is disengaged while the start gear400 is engaged with a ring gear 600 (see FIG. 2).

That is, an ISG system serves as a starter motor in order for the engine1 to start or restart. In this case, since the RPM of the engine 1 isnot high, it is not desired to drive a balance shaft 300. Accordingly,in order to block the rotational force of a motor 100 from beingtransferred to the balance shaft 300, the clutch 200 is disengaged.Therefore, it is possible to inhibit or prevent undesired energyconsumption and improve the fuel efficiency of a vehicle.

The method of controlling a motor assembly for starting an engine anddriving a balance shaft includes a second operation step of stopping theoperation of the actuator 500 such that the motor shaft 110 is movedbackward (S400) when it is not desired to start or restart the engine 1.In step S400, the clutch 200 is engaged while the start gear 400 isdisengaged from the ring gear 600 (see FIGS. 3 and 4).

That is, since the engine 1 is not required to start or restart, the ISGsystem is prepared to serve as a motor for driving the balance shaft300, instead of serving as a starter motor. In this case, since theunbalanced weight of the balance shaft 300 is always directed downwardby gravity, the rotational angular phase of the unbalanced weight isconstant when the clutch 200 is engaged. Therefore, it is possible tostably control an anti-phase relative to the unbalanced force of theengine.

The method of controlling a motor assembly for starting an engine anddriving a balance shaft may include a second determination step ofdetermining whether the RPM of the engine 1 is less than thepredetermined target RPM (S500) after the second operation step (S400).In addition, the method may include a step of driving the balance shaft300 by rotating the motor 100 (S600) when the RPM of the engine 1 isequal to or higher than the predetermined target RPM (see FIG. 4).

That is, when the RPM of the engine 1 is equal to or higher than thepredetermined target RPM, the balance shaft 300 is driven in order tocancel out the unbalanced inertia force of the engine. In this case, thepredetermined target RPM may be set to be different according to thetype of vehicle (e.g. the predetermined target RPM may be set as 3500RPM).

On the other hand, when the RPM of the engine 1 is less than thepredetermined target RPM, the motor 100 is stopped, and thus the balanceshaft 300 is also stopped. In this case, since the noise (e.g., boomingnoise) and vibration of the vehicle are not great enough, there is noneed to drive the balance shaft 300. Therefore, it is possible toinhibit or prevent undesired energy consumption and improve the fuelefficiency of the vehicle (see FIG. 3).

In accordance with the exemplary forms of the present disclosure, sincea separate motor for driving a balance shaft is removed from a motorassembly, it is possible to reduce the cost and weight of a vehicle.

When an engine RPM is low, the driving of the balance shaft is stoppedso that fuel efficiency can be improved. On the other hand, when theengine RPM is high, the balance shaft is driven so that excellent NVH(Noise, Vibration, and Harshness) performance can be maintained.

While the present disclosure has been described with respect to thespecific forms, it will be apparent to those skilled in the art thatvarious changes and modifications may be made without departing from thespirit and scope of the present disclosure as defined in the followingclaims.

What is claimed is:
 1. A method of controlling a motor assembly forstarting an engine and driving a balance shaft, comprising: determiningwhether starting or restarting of an engine is desired; operating anactuator such that a motor shaft is moved forward when the starting orrestarting of the engine is desired; and starting or restarting theengine by rotating a motor and by driving a start gear, after theoperating the actuator.
 2. The method of claim 1, wherein, in theoperating the actuator, a clutch is disengaged while the start gear isengaged with a ring gear.
 3. The method of claim 1, further comprisingstopping the operation of the actuator such that the motor shaft ismoved backward when the starting or restarting of the engine isundesired.
 4. The method of claim 3, wherein, in the stopping operationof the actuator, a clutch is engaged while the start gear is disengagedfrom a ring gear.
 5. The method of claim 3, further comprisingdetermining whether an RPM of the engine is less than a predeterminedtarget RPM, after the stopping operation of the actuator.
 6. The methodof claim 5, further comprising driving a balance shaft by rotating themotor when the RPM of the engine is equal to or higher than thepredetermined target RPM.